We have prepared 100-fold enriched sarcolemmal membranes from isolated adult canine cardiac myocytes. We have shown activation of the Na ion, K ion)-ATPase by lysolecithin; dramatic inhibition of enriched microsomal rotenone-insensitive NADH cytochrome c reductase by lysolecithin has been found as well. With less enriched sarcolemma (8-fold) we reported the presence of endogenous phospholipase A which is stimulated by isoproterenol and inhibited by propranolol. In addition, exogenous phospholipase A2 attacks sarcolemmal ethanolamine phospholipid preferentially. We have continued to study perturbations of latency of cardiac and hepatic lysosomes by hypo- and hyperosmolar salts. Chlorpromazine inhibits dramatically the production in vitro of free fatty acids and lysophospholipids by lysosomal lipases. Using free-flow electrophoresis we have succeeded in obtaining 100-fold enriched "native" hepatic lysosomes and 150-fold enriched "tritosomes" for assay of lipolytic enzymes. We plan to extend this technique to purification of cardiac sarcolemma, "microsomes" and lysosomes for more precise studies of myocardial organelle lipid structure and function.